The present application is directed to interface circuits for lighting systems. It finds particular application in conjunction with low power control modules that receive hardwire signals from sensors, which are relayed wirelessly to high level controllers within a system architecture to facilitate control within lighting systems, and will be described with particular reference thereto. It is to be appreciated, however, that the present exemplary embodiments are also amenable to other like applications.
Lighting control systems are frequently used to provide illumination to industrial buildings, commercial structures and other large spaces. Conventional lighting control systems include a user interface, a controller, a power supply, light sources (e.g., incandescent, florescent, etc.) and cable to couple the light sources to the controller and the power supply. The user interface can be employed to allow a user to turn on, turn off and dim light sources within the system by interfacing to the power supply and/or a ballast/driver associated with power delivery to the light sources. A user can program lighting levels based upon one or more conditions such as a time of day, room occupancy, presence/absence of daylight, an event, an alarm and/or any combination of these conditions.
Fluorescent light sources are a popular choice to use within lighting control systems as they have many advantages over incandescent light sources. For example, fluorescent light sources can convert ten times more input power to visible light than incandescent light sources. In addition, a fluorescent light source lasts ten to twenty times as long as an equivalent incandescent light source when operated several hours at a time. Compared with an incandescent light source, a fluorescent tube is a more diffuse and physically larger light source. Thus, light can be more evenly distributed without point source of glare such as seen from an undiffused incandescent filament. Moreover, two-thirds to three-quarters less heat is given off by fluorescent light sources compared to an equivalent installation of incandescent light sources. This greatly reduces the size, cost, and energy consumption of lighting equipment.
Lighting systems can be controlled by analog and/or digital control protocols communicated via a hardwire network. In one example, an analog hardwire control system varies between 0-10VDC to provide simple control to the devices within the system. The controlled lighting can be scaled such that at 10V, light sources are around 100 percent of potential output, and at 0 volts are at around 0 percent output (off). With fluorescent light sources, this analog control is provided to the ballast/driver to adjust the light output as desired. Dimming devices can also be designed to respond in various patterns to intermediate voltages, wherein output curves are linear for voltage output, actual light output, power output and/or perceived light output.
Hardwire control systems can require significant expense related to installation and maintenance within a lighting system. In one example, control of ballast/drivers and associated lighting within a building can require several thousand feet of cabling, mounting brackets, apertures, etc. Moreover, use of a physical connection to communicate with each ballast/driver and/or light source brings inherent problems associated with material breakdown and/or failure. In one example, conventional control system components, such as ballast/drivers, require high voltage (e.g., 277 VAC) to operate. These high voltage lines often require housing in a conduit and/or other safety measures, which can limit the location of components coupled thereto. Accordingly, increased costs can be incurred for additional materials, rerouting power and/or control lines, redesign of layout, etc.
Thus, systems and methods are needed to overcome the above-referenced problems with hardwire networks used with lighting control systems and others.